The feature works with any Miracast and DLNA device, according to a blog post on the news from Gabe Aul, vice president of engineering systems in Microsoft’s Windows and Devices Group. Here’s Aul showing how it works for different kinds of content:

Cast a video from YouTube: Go to YouTube.com in Microsoft Edge. Click on the “…” menu and the top left, and select “Cast media to device” and select the Miracast or DLNA device you want to cast to.
Cast a Facebook photo album: Login to Facebook in Microsoft Edge and click on the first photo in one of your photo albums to cast. Click on the “…” menu and the top left, and select “Cast media to device” and select the Miracast or DLNA device you want to cast to. Navigate through your photo album by clicking on the forward and backward buttons.
Cast your music from Pandora: Login to Pandora in Microsoft Edge to get to your music and click on the “…” menu and the top left, and select “Cast media to device” and select the Miracast or DLNA device you want to cast to.

This is an exciting feature to ship in a Windows preview build, for sure — but there is a caveat.

In addition to media casting in Edge, Microsoft has also made Cortana a little bit more powerful in Edge — now you can select the Ask Cortana button in the right-click menu while you’re looking at PDFs in the browser.

Other updates include performance improvements for nested virtualization in Hyper-V Containers, improved memory usage for the Xbox app in certain scenarios, and the temporary removal of the VP9 video codec.

Read the full blog post for a complete list of changes in this build. And if you aren’t yet part of Microsoft’s Windows Insider Program, you can sign up to get the latest in Windows 10